[unix-history] / usr / src / old / regexp / regexp.c

#include <ctype.h>

typedef int	boolean;
#define TRUE	1
#define FALSE	0
#define NIL	0

boolean l_onecase;	/* true if upper and lower equivalent */

#define makelower(c) (isupper((c)) ? tolower((c)) : (c))

/*  STRNCMP -	like strncmp except that we convert the
 *	 	first string to lower case before comparing
 *		if l_onecase is set.
 */

STRNCMP(s1, s2, len)
	register char *s1,*s2;
	register int len;
{
	if (l_onecase) {
	    do
		if (*s2 - makelower(*s1))
			return (*s2 - makelower(*s1));
		else {
			s2++;
			s1++;
		}
	    while (--len);
	} else {
	    do
		if (*s2 - *s1)
			return (*s2 - *s1);
		else {
			s2++;
			s1++;
		}
	    while (--len);
	}
	return(0);
}

/*	The following routine converts an irregular expression to
 *	internal format.
 *
 *	Either meta symbols (\a \d or \p) or character strings or
 *	operations ( alternation or perenthesizing ) can be
 *	specified.  Each starts with a descriptor byte.  The descriptor
 *	byte has STR set for strings, META set for meta symbols
 *	and OPER set for operations.
 *	The descriptor byte can also have the OPT bit set if the object
 *	defined is optional.  Also ALT can be set to indicate an alternation.
 *
 *	For metasymbols the byte following the descriptor byte identities
 *	the meta symbol (containing an ascii 'a', 'd', 'p', '|', or '(').  For
 *	strings the byte after the descriptor is a character count for
 *	the string:
 *
 *		meta symbols := descriptor
 *				symbol
 *
 *		strings :=	descriptor
 *				character count
 *				the string
 *
 *		operatins :=	descriptor
 *				symbol
 *				character count
 */

/*
 *  handy macros for accessing parts of match blocks
 */
#define MSYM(A) (*(A+1))	/* symbol in a meta symbol block */
#define MNEXT(A) (A+2)		/* character following a metasymbol block */

#define OSYM(A) (*(A+1))	/* symbol in an operation block */
#define OCNT(A) (*(A+2))	/* character count */
#define ONEXT(A) (A+3)		/* next character after the operation */
#define OPTR(A) (A+*(A+2))	/* place pointed to by the operator */

#define SCNT(A) (*(A+1))	/* byte count of a string */
#define SSTR(A) (A+2)		/* address of the string */
#define SNEXT(A) (A+2+*(A+1))	/* character following the string */

/*
 *  bit flags in the descriptor 
 */
#define OPT 1
#define STR 2
#define META 4
#define ALT 8
#define OPER 16

char *ure;		/* pointer current position in unconverted exp */
char *ccre;		/* pointer to current position in converted exp*/
char *malloc();

char *
convexp(re)
    char *re;		/* unconverted irregular expression */
{
    register char *cre;		/* pointer to converted regular expression */

    /* allocate room for the converted expression */
    if (re == NIL)
	return (NIL);
    if (*re == '\0')
	return (NIL);
    cre = malloc (4 * strlen(re) + 3);
    ccre = cre;
    ure = re;

    /* start the conversion with a \a */
    *cre = META | OPT;
    MSYM(cre) = 'a';
    ccre = MNEXT(cre);

    /* start the conversion (its recursive) */
    expconv ();
    *ccre = 0;
    return (cre);
}

expconv()
{
    register char *cs;		/* pointer to current symbol in converted exp */
    register char c;		/* character being processed */
    register char *acs;		/* pinter to last alternate */
    register int temp;

    /* let the conversion begin */
    acs = NIL;
    while (*ure != NIL) {
	switch (c = *ure++) {

	case '\\':
	    switch (c = *ure++) {

	    /* escaped characters are just characters */
	    default:
		if ((*cs & STR) == 0) {
		    cs = ccre;
		    *cs = STR;
		    SCNT(cs) = 1;
		    ccre += 2;
		} else 
		    SCNT(cs)++;
		*ccre++ = c;
		break;

	    /* normal(?) metacharacters */
	    case 'a':
	    case 'd':
	    case 'e':
	    case 'p':
		if (acs != NIL && acs != cs) {
		    do {
			temp = OCNT(acs);
			OCNT(acs) = ccre - acs; 
			acs -= temp;
		    } while (temp != 0);
		    acs = NIL;
		}
		cs = ccre;
		*cs = META;
		MSYM(cs) = c;
		ccre = MNEXT(cs);
		break;
	    }
	    break;
	    
	/* just put the symbol in */
	case '^':
	case '$':
	    if (acs != NIL && acs != cs) {
		do {
		    temp = OCNT(acs);
		    OCNT(acs) = ccre - acs;
		    acs -= temp;
		} while (temp != 0);
		acs = NIL;
	    }
	    cs = ccre;
	    *cs = META;
	    MSYM(cs) = c;
	    ccre = MNEXT(cs);
	    break;

	/* mark the last match sequence as optional */
	case '?':
	    *cs = *cs | OPT;
	    break;

	/* recurse and define a subexpression */
	case '(':
	    if (acs != NIL && acs != cs) {
		do {
		    temp = OCNT(acs);
		    OCNT(acs) = ccre - acs;
		    acs -= temp;
		} while (temp != 0);
		acs = NIL;
	    }
	    cs = ccre;
	    *cs = OPER;
	    OSYM(cs) = '(';
	    ccre = ONEXT(cs);
	    expconv ();
	    OCNT(cs) = ccre - cs;		/* offset to next symbol */
	    break;

	/* return from a recursion */
	case ')':
	    if (acs != NIL) {
		do {
		    temp = OCNT(acs);
		    OCNT(acs) = ccre - acs;
		    acs -= temp;
		} while (temp != 0);
		acs = NIL;
	    }
	    cs = ccre;
	    *cs = META;
	    MSYM(cs) = c;
	    ccre = MNEXT(cs);
	    return;

	/* mark the last match sequence as having an alternate */
	/* the third byte will contain an offset to jump over the */
	/* alternate match in case the first did not fail */
	case '|':
	    if (acs != NIL && acs != cs)
		OCNT(ccre) = ccre - acs;	/* make a back pointer */
	    else
		OCNT(ccre) = 0;
	    *cs |= ALT;
	    cs = ccre;
	    *cs = OPER;
	    OSYM(cs) = '|';
	    ccre = ONEXT(cs);
	    acs = cs;	/* remember that the pointer is to be filles */
	    break;

	/* if its not a metasymbol just build a scharacter string */
	default:
	    if ((*cs & STR) == 0) {
		cs = ccre;
		*cs = STR;
		SCNT(cs) = 1;
		ccre = SSTR(cs);
	    } else
		SCNT(cs)++;
	    *ccre++ = c;
	    break;
	}
    }
    if (acs != NIL) {
	do {
	    temp = OCNT(acs);
	    OCNT(acs) = ccre - acs;
	    acs -= temp;
	} while (temp != 0);
	acs = NIL;
    }
    return;
}
/* end of convertre */


/*
 *	The following routine recognises an irregular expresion
 *	with the following special characters:
 *
 *		\?	-	means last match was optional
 *		\a	-	matches any number of characters
 *		\d	-	matches any number of spaces and tabs
 *		\p	-	matches any number of alphanumeric
 *				characters. The
 *				characters matched will be copied into
 *				the area pointed to by 'name'.
 *		\|	-	alternation
 *		\( \)	-	grouping used mostly for alternation and
 *				optionality
 *
 *	The irregular expression must be translated to internal form
 *	prior to calling this routine
 *
 *	The value returned is the pointer to the first non \a 
 *	character matched.
 */

boolean _escaped;		/* true if we are currently _escaped */
char *_start;			/* start of string */

char *
expmatch (s, re, mstring)
    register char *s;		/* string to check for a match in */
    register char *re;		/* a converted irregular expression */
    register char *mstring;	/* where to put whatever matches a \p */
{
    register char *cs;		/* the current symbol */
    register char *ptr,*s1;	/* temporary pointer */
    boolean matched;		/* a temporary boolean */

    /* initial conditions */
    if (re == NIL)
	return (NIL);
    cs = re;
    matched = FALSE;

    /* loop till expression string is exhausted (or at least pretty tired) */
    while (*cs) {
	switch (*cs & (OPER | STR | META)) {

	/* try to match a string */
	case STR:
	    matched = !STRNCMP (s, SSTR(cs), SCNT(cs));
	    if (matched) {

		/* hoorah it matches */
		s += SCNT(cs);
		cs = SNEXT(cs);
	    } else if (*cs & ALT) {

		/* alternation, skip to next expression */
		cs = SNEXT(cs);
	    } else if (*cs & OPT) {

		/* the match is optional */
		cs = SNEXT(cs);
		matched = 1;		/* indicate a successful match */
	    } else {

		/* no match, error return */
		return (NIL);
	    }
	    break;

	/* an operator, do something fancy */
	case OPER:
	    switch (OSYM(cs)) {

	    /* this is an alternation */
	    case '|':
		if (matched)

		    /* last thing in the alternation was a match, skip ahead */
		    cs = OPTR(cs);
		else

		    /* no match, keep trying */
		    cs = ONEXT(cs);
		break;

	    /* this is a grouping, recurse */
	    case '(':
		ptr = expmatch (s, ONEXT(cs), mstring);
		if (ptr != NIL) {

		    /* the subexpression matched */
		    matched = 1;
		    s = ptr;
		} else if (*cs & ALT) {

		    /* alternation, skip to next expression */
		    matched = 0;
		} else if (*cs & OPT) {

		    /* the match is optional */
		    matched = 1;	/* indicate a successful match */
		} else {

		    /* no match, error return */
		    return (NIL);
		}
		cs = OPTR(cs);
		break;
	    }
	    break;

	/* try to match a metasymbol */
	case META:
	    switch (MSYM(cs)) {

	    /* try to match anything and remember what was matched */
	    case 'p':
		/*
		 *  This is really the same as trying the match the
		 *  remaining parts of the expression to any subset
		 *  of the string.
		 */
		s1 = s;
		do {
		    ptr = expmatch (s1, MNEXT(cs), mstring);
		    if (ptr != NIL && s1 != s) {

			/* we have a match, remember the match */
			strncpy (mstring, s, s1 - s);
			mstring[s1 - s] = '\0';
			return (ptr);
		    } else if (ptr != NIL && (*cs & OPT)) {

			/* it was aoptional so no match is ok */
			return (ptr);
		    } else if (ptr != NIL) {

			/* not optional and we still matched */
			return (NIL);
		    }
		    if (!isalnum(*s1) && *s1 != '_')
			return (NIL);
		    if (*s1 == '\\')
			_escaped = _escaped ? FALSE : TRUE;
		    else
			_escaped = FALSE;
		} while (*s1++);
		return (NIL);

	    /* try to match anything */
	    case 'a':
		/*
		 *  This is really the same as trying the match the
		 *  remaining parts of the expression to any subset
		 *  of the string.
		 */
		s1 = s;
		do {
		    ptr = expmatch (s1, MNEXT(cs), mstring);
		    if (ptr != NIL && s1 != s) {

			/* we have a match */
			return (ptr);
		    } else if (ptr != NIL && (*cs & OPT)) {

			/* it was aoptional so no match is ok */
			return (ptr);
		    } else if (ptr != NIL) {

			/* not optional and we still matched */
			return (NIL);
		    }
		    if (*s1 == '\\')
			_escaped = _escaped ? FALSE : TRUE;
		    else
			_escaped = FALSE;
		} while (*s1++);
		return (NIL);

	    /* fail if we are currently _escaped */
	    case 'e':
		if (_escaped)
		    return(NIL);
		cs = MNEXT(cs); 
		break;

	    /* match any number of tabs and spaces */
	    case 'd':
		ptr = s;
		while (*s == ' ' || *s == '\t')
		    s++;
		if (s != ptr || s == _start) {

		    /* match, be happy */
		    matched = 1;
		    cs = MNEXT(cs); 
		} else if (*s == '\n' || *s == '\0') {

		    /* match, be happy */
		    matched = 1;
		    cs = MNEXT(cs); 
		} else if (*cs & ALT) {

		    /* try the next part */
		    matched = 0;
		    cs = MNEXT(cs);
		} else if (*cs & OPT) {

		    /* doesn't matter */
		    matched = 1;
		    cs = MNEXT(cs);
		} else

		    /* no match, error return */
		    return (NIL);
		break;

	    /* check for end of line */
	    case '$':
		if (*s == '\0' || *s == '\n') {

		    /* match, be happy */
		    s++;
		    matched = 1;
		    cs = MNEXT(cs);
		} else if (*cs & ALT) {

		    /* try the next part */
		    matched = 0;
		    cs = MNEXT(cs);
		} else if (*cs & OPT) {

		    /* doesn't matter */
		    matched = 1;
		    cs = MNEXT(cs);
		} else

		    /* no match, error return */
		    return (NIL);
		break;

	    /* check for start of line */
	    case '^':
		if (s == _start) {

		    /* match, be happy */
		    matched = 1;
		    cs = MNEXT(cs);
		} else if (*cs & ALT) {

		    /* try the next part */
		    matched = 0;
		    cs = MNEXT(cs);
		} else if (*cs & OPT) {

		    /* doesn't matter */
		    matched = 1;
		    cs = MNEXT(cs);
		} else

		    /* no match, error return */
		    return (NIL);
		break;

	    /* end of a subexpression, return success */
	    case ')':
		return (s);
	    }
	    break;
	}
    }
    return (s);
}
Commit	Line	Data
0df031ff BJ	1	#include <ctype.h>
	2
	3	typedef int boolean;
	4	#define TRUE 1
	5	#define FALSE 0
	6	#define NIL 0
	7
	8	boolean l_onecase; /* true if upper and lower equivalent */
	9
	10	#define makelower(c) (isupper((c)) ? tolower((c)) : (c))
	11
	12	/* STRNCMP - like strncmp except that we convert the
	13	* first string to lower case before comparing
	14	* if l_onecase is set.
	15	*/
	16
	17	STRNCMP(s1, s2, len)
	18	register char s1,s2;
	19	register int len;
	20	{
	21	if (l_onecase) {
	22	do
	23	if (s2 - makelower(s1))
	24	return (s2 - makelower(s1));
	25	else {
	26	s2++;
	27	s1++;
	28	}
	29	while (--len);
	30	} else {
	31	do
	32	if (s2 - s1)
	33	return (s2 - s1);
	34	else {
	35	s2++;
	36	s1++;
	37	}
	38	while (--len);
	39	}
	40	return(0);
	41	}
	42
	43	/* The following routine converts an irregular expression to
	44	* internal format.
	45	*
	46	* Either meta symbols (\a \d or \p) or character strings or
	47	* operations ( alternation or perenthesizing ) can be
	48	* specified. Each starts with a descriptor byte. The descriptor
	49	* byte has STR set for strings, META set for meta symbols
	50	* and OPER set for operations.
	51	* The descriptor byte can also have the OPT bit set if the object
	52	* defined is optional. Also ALT can be set to indicate an alternation.
	53	*
	54	* For metasymbols the byte following the descriptor byte identities
	55	* the meta symbol (containing an ascii 'a', 'd', 'p', '\|', or '('). For
	56	* strings the byte after the descriptor is a character count for
	57	* the string:
	58	*
	59	* meta symbols := descriptor
	60	* symbol
	61	*
	62	* strings := descriptor
	63	* character count
	64	* the string
65	*
66	* operatins := descriptor
67	* symbol
68	* character count
69	*/
70
71	/*
72	* handy macros for accessing parts of match blocks
73	*/
74	#define MSYM(A) ((A+1)) / symbol in a meta symbol block */
75	#define MNEXT(A) (A+2) /* character following a metasymbol block */
76
77	#define OSYM(A) ((A+1)) / symbol in an operation block */
78	#define OCNT(A) ((A+2)) / character count */
79	#define ONEXT(A) (A+3) /* next character after the operation */
80	#define OPTR(A) (A+(A+2)) / place pointed to by the operator */
81
82	#define SCNT(A) ((A+1)) / byte count of a string */
83	#define SSTR(A) (A+2) /* address of the string */
84	#define SNEXT(A) (A+2+(A+1)) / character following the string */
85
86	/*
87	* bit flags in the descriptor
88	*/
89	#define OPT 1
90	#define STR 2
91	#define META 4
92	#define ALT 8
93	#define OPER 16
94
95	char ure; / pointer current position in unconverted exp */
96	char ccre; / pointer to current position in converted exp*/
97	char *malloc();
98
99	char *
100	convexp(re)
101	char re; / unconverted irregular expression */
102	{
103	register char cre; / pointer to converted regular expression */
104
105	/* allocate room for the converted expression */
106	if (re == NIL)
107	return (NIL);
108	if (*re == '\0')
109	return (NIL);
110	cre = malloc (4 * strlen(re) + 3);
111	ccre = cre;
112	ure = re;
113
114	/* start the conversion with a \a */
115	*cre = META \| OPT;
116	MSYM(cre) = 'a';
117	ccre = MNEXT(cre);
118
119	/* start the conversion (its recursive) */
120	expconv ();
121	*ccre = 0;
122	return (cre);
123	}
124
125	expconv()
126	{
127	register char cs; / pointer to current symbol in converted exp */
128	register char c; /* character being processed */
129	register char acs; / pinter to last alternate */
130	register int temp;
131
132	/* let the conversion begin */
133	acs = NIL;
134	while (*ure != NIL) {
135	switch (c = *ure++) {
136
137	case '\\':
138	switch (c = *ure++) {
139
140	/* escaped characters are just characters */
141	default:
142	if ((*cs & STR) == 0) {
143	cs = ccre;
144	*cs = STR;
145	SCNT(cs) = 1;
146	ccre += 2;
147	} else
148	SCNT(cs)++;
149	*ccre++ = c;
150	break;
151
152	/* normal(?) metacharacters */
153	case 'a':
154	case 'd':
155	case 'e':
156	case 'p':
157	if (acs != NIL && acs != cs) {
158	do {
159	temp = OCNT(acs);
160	OCNT(acs) = ccre - acs;
161	acs -= temp;
162	} while (temp != 0);
163	acs = NIL;
164	}
165	cs = ccre;
166	*cs = META;
167	MSYM(cs) = c;
168	ccre = MNEXT(cs);
169	break;
170	}
171	break;
172
173	/* just put the symbol in */
174	case '^':
175	case '$':
176	if (acs != NIL && acs != cs) {
177	do {
178	temp = OCNT(acs);
179	OCNT(acs) = ccre - acs;
180	acs -= temp;
181	} while (temp != 0);
182	acs = NIL;
183	}
184	cs = ccre;
185	*cs = META;
186	MSYM(cs) = c;
187	ccre = MNEXT(cs);
188	break;
189
190	/* mark the last match sequence as optional */
191	case '?':
192	cs = cs \| OPT;
193	break;
194
195	/* recurse and define a subexpression */
196	case '(':
197	if (acs != NIL && acs != cs) {
198	do {
199	temp = OCNT(acs);
200	OCNT(acs) = ccre - acs;
201	acs -= temp;
202	} while (temp != 0);
203	acs = NIL;
204	}
205	cs = ccre;
206	*cs = OPER;
207	OSYM(cs) = '(';
208	ccre = ONEXT(cs);
209	expconv ();
210	OCNT(cs) = ccre - cs; /* offset to next symbol */
211	break;
212
213	/* return from a recursion */
214	case ')':
215	if (acs != NIL) {
216	do {
217	temp = OCNT(acs);
218	OCNT(acs) = ccre - acs;
219	acs -= temp;
220	} while (temp != 0);
221	acs = NIL;
222	}
223	cs = ccre;
224	*cs = META;
225	MSYM(cs) = c;
226	ccre = MNEXT(cs);
227	return;
228
229	/* mark the last match sequence as having an alternate */
230	/* the third byte will contain an offset to jump over the */
231	/* alternate match in case the first did not fail */
232	case '\|':
233	if (acs != NIL && acs != cs)
234	OCNT(ccre) = ccre - acs; /* make a back pointer */
235	else
236	OCNT(ccre) = 0;
237	*cs \|= ALT;
238	cs = ccre;
239	*cs = OPER;
240	OSYM(cs) = '\|';
241	ccre = ONEXT(cs);
242	acs = cs; /* remember that the pointer is to be filles */
243	break;
244
245	/* if its not a metasymbol just build a scharacter string */
246	default:
247	if ((*cs & STR) == 0) {
248	cs = ccre;
249	*cs = STR;
250	SCNT(cs) = 1;
251	ccre = SSTR(cs);
252	} else
253	SCNT(cs)++;
254	*ccre++ = c;
255	break;
256	}
257	}
258	if (acs != NIL) {
259	do {
260	temp = OCNT(acs);
261	OCNT(acs) = ccre - acs;
262	acs -= temp;
263	} while (temp != 0);
264	acs = NIL;
265	}
266	return;
267	}
268	/* end of convertre */
269
270
271	/*
272	* The following routine recognises an irregular expresion
273	* with the following special characters:
274	*
275	* \? - means last match was optional
276	* \a - matches any number of characters
277	* \d - matches any number of spaces and tabs
278	* \p - matches any number of alphanumeric
279	* characters. The
280	* characters matched will be copied into
281	* the area pointed to by 'name'.
282	* \\| - alternation
283	* \( \) - grouping used mostly for alternation and
284	* optionality
285	*
286	* The irregular expression must be translated to internal form
287	* prior to calling this routine
288	*
289	* The value returned is the pointer to the first non \a
290	* character matched.
291	*/
292
293	boolean _escaped; /* true if we are currently _escaped */
294	char _start; / start of string */
295
296	char *
297	expmatch (s, re, mstring)
298	register char s; / string to check for a match in */
299	register char re; / a converted irregular expression */
300	register char mstring; / where to put whatever matches a \p */
301	{
302	register char cs; / the current symbol */
303	register char ptr,s1; /* temporary pointer */
304	boolean matched; /* a temporary boolean */
305
306	/* initial conditions */
307	if (re == NIL)
308	return (NIL);
309	cs = re;
310	matched = FALSE;
311
312	/* loop till expression string is exhausted (or at least pretty tired) */
313	while (*cs) {
314	switch (*cs & (OPER \| STR \| META)) {
315
316	/* try to match a string */
317	case STR:
318	matched = !STRNCMP (s, SSTR(cs), SCNT(cs));
319	if (matched) {
320
321	/* hoorah it matches */
322	s += SCNT(cs);
323	cs = SNEXT(cs);
324	} else if (*cs & ALT) {
325
326	/* alternation, skip to next expression */
327	cs = SNEXT(cs);
328	} else if (*cs & OPT) {
329
330	/* the match is optional */
331	cs = SNEXT(cs);
332	matched = 1; /* indicate a successful match */
333	} else {
334
335	/* no match, error return */
336	return (NIL);
337	}
338	break;
339
340	/* an operator, do something fancy */
341	case OPER:
342	switch (OSYM(cs)) {
343
344	/* this is an alternation */
345	case '\|':
346	if (matched)
347
348	/* last thing in the alternation was a match, skip ahead */
349	cs = OPTR(cs);
350	else
351
352	/* no match, keep trying */
353	cs = ONEXT(cs);
354	break;
355
356	/* this is a grouping, recurse */
357	case '(':
358	ptr = expmatch (s, ONEXT(cs), mstring);
359	if (ptr != NIL) {
360
361	/* the subexpression matched */
362	matched = 1;
363	s = ptr;
364	} else if (*cs & ALT) {
365
366	/* alternation, skip to next expression */
367	matched = 0;
368	} else if (*cs & OPT) {
369
370	/* the match is optional */
371	matched = 1; /* indicate a successful match */
372	} else {
373
374	/* no match, error return */
375	return (NIL);
376	}
377	cs = OPTR(cs);
378	break;
379	}
380	break;
381
382	/* try to match a metasymbol */
383	case META:
384	switch (MSYM(cs)) {
385
386	/* try to match anything and remember what was matched */
387	case 'p':
388	/*
389	* This is really the same as trying the match the
390	* remaining parts of the expression to any subset
391	* of the string.
392	*/
393	s1 = s;
394	do {
395	ptr = expmatch (s1, MNEXT(cs), mstring);
396	if (ptr != NIL && s1 != s) {
397
398	/* we have a match, remember the match */
399	strncpy (mstring, s, s1 - s);
400	mstring[s1 - s] = '\0';
401	return (ptr);
402	} else if (ptr != NIL && (*cs & OPT)) {
403
404	/* it was aoptional so no match is ok */
405	return (ptr);
406	} else if (ptr != NIL) {
407
408	/* not optional and we still matched */
409	return (NIL);
410	}
411	if (!isalnum(s1) && s1 != '_')
412	return (NIL);
413	if (*s1 == '\\')
414	_escaped = _escaped ? FALSE : TRUE;
415	else
416	_escaped = FALSE;
417	} while (*s1++);
418	return (NIL);
419
420	/* try to match anything */
421	case 'a':
422	/*
423	* This is really the same as trying the match the
424	* remaining parts of the expression to any subset
425	* of the string.
426	*/
427	s1 = s;
428	do {
429	ptr = expmatch (s1, MNEXT(cs), mstring);
430	if (ptr != NIL && s1 != s) {
431
432	/* we have a match */
433	return (ptr);
434	} else if (ptr != NIL && (*cs & OPT)) {
435
436	/* it was aoptional so no match is ok */
437	return (ptr);
438	} else if (ptr != NIL) {
439
440	/* not optional and we still matched */
441	return (NIL);
442	}
443	if (*s1 == '\\')
444	_escaped = _escaped ? FALSE : TRUE;
445	else
446	_escaped = FALSE;
447	} while (*s1++);
448	return (NIL);
449
450	/* fail if we are currently _escaped */
451	case 'e':
452	if (_escaped)
453	return(NIL);
454	cs = MNEXT(cs);
455	break;
456
457	/* match any number of tabs and spaces */
458	case 'd':
459	ptr = s;
460	while (s == ' ' \|\| s == '\t')
461	s++;
462	if (s != ptr \|\| s == _start) {
463
464	/* match, be happy */
465	matched = 1;
466	cs = MNEXT(cs);
467	} else if (s == '\n' \|\| s == '\0') {
468
469	/* match, be happy */
470	matched = 1;
471	cs = MNEXT(cs);
472	} else if (*cs & ALT) {
473
474	/* try the next part */
475	matched = 0;
476	cs = MNEXT(cs);
477	} else if (*cs & OPT) {
478
479	/* doesn't matter */
480	matched = 1;
481	cs = MNEXT(cs);
482	} else
483
484	/* no match, error return */
485	return (NIL);
486	break;
487
488	/* check for end of line */
489	case '$':
490	if (s == '\0' \|\| s == '\n') {
491
492	/* match, be happy */
493	s++;
494	matched = 1;
495	cs = MNEXT(cs);
496	} else if (*cs & ALT) {
497
498	/* try the next part */
499	matched = 0;
500	cs = MNEXT(cs);
501	} else if (*cs & OPT) {
502
503	/* doesn't matter */
504	matched = 1;
505	cs = MNEXT(cs);
506	} else
507
508	/* no match, error return */
509	return (NIL);
510	break;
511
512	/* check for start of line */
513	case '^':
514	if (s == _start) {
515
516	/* match, be happy */
517	matched = 1;
518	cs = MNEXT(cs);
519	} else if (*cs & ALT) {
520
521	/* try the next part */
522	matched = 0;
523	cs = MNEXT(cs);
524	} else if (*cs & OPT) {
525
526	/* doesn't matter */
527	matched = 1;
528	cs = MNEXT(cs);
529	} else
530
531	/* no match, error return */
532	return (NIL);
533	break;
534
535	/* end of a subexpression, return success */
536	case ')':
537	return (s);
538	}
539	break;
540	}
541	}
542	return (s);
543	}